Subbing solution for photographic films



Patented July 13, 1943 2,324,105 SUBBING SOLUTION FOR PHOTOGRAPHIC FILMSGale F. Nadeau and Louis 1:. Eilers, Rochester, N. Y., assignors toEastman Kodak Company Rochester, N. Y., a corporation of New Jersey NoDrawing: Application September 25, 1940, Serial No. 358,275

11 Claims.

This invention relates to the manufacture of photographic materials, andmore particularly to the preparation of gelatin subbing solutions inwhich the gelatin is dispersed therein by meansof various easilydecomposable tetraalkyl ammonium hydroxides.

In the manufacture of photographic film it is necessary to deposit onthe usual cellulose derivative support or film base an extremely thincoating of gelatin in order to prepare the surface of the material forthe permanent adhesion of the light-sensitive emulsion thereto. It isknown that the keeping qualities and other properties of the finishedfilmare dependent to a very great extent upon the nature of the gel suband the manner in which it is applied to the support. It is accordinglya matter pf prime importance that the gelatin be uniformly dispersed inthe subbing solution and that the dispersing a ent be of such naturethat it will not adversely affect-the properties of the finished film,nor interfere with the process of manufacture.

Many different dispersing agents have heretofore been used for thispurpose, but all have possessed certain serious drawbacks which havemade their use inconvenient or expensive. For example, the use ofvolatile acids has been suggested, but it is found that they aredisadvantageous because of the fact that they volatilize during thesubbing operation and corrode the film making machinery and the solventrecovery system which is customarily a part thereof. In order toovercome this d-iificulty it has been proposed to use certainnon-volatile acids, but the use of such agents has the seriousdisadvantage that the acid remains in the gel sub and exerts adestructive or desensitizing action on the sensitive emulsion.

The present invention has as an object to overcome the above-mentionedprior art difficulties and to provide a method of dispersing gelatin ina subbing solution by means of dispersing agents These objects areaccomplished by the following invention which, in its broader aspects,comprises the use as dispersing agents in gel subbing solution ofvarious tetraalkyl ammonium hydroxides which, although stable atordinary room temperatures, are, nevertheless, easily decomposable intovolatile or non-volatile, non-corrosive compounds at temperaturesgenerally employed in themanufacture and the subbing of photographicfilm support and makes possible the preparation of a sub whose pH isnear or equal to that of the emulsion for which the base is intended.Among these hydroxides may be mentioned trimethyl benzyl ammoniumhydroxide and tetramethyl ammonium hydroxide. The decomposition productsare tertiary amines and alcohols, none of which affect the sensitivityof emulsions in contact with them and in addition they maintain the pHlevel of the subbing layer near or equal to that of the emulsion.

In the following examples and descriptions we .have set forth several ofthe preferred embodi- Example 1 Per cent Gelatin 1.0

Trimethyl benzyl ammonium hydroxide 0.05 Water 5.0 Acetone 65.95Methanol 28.0

This solution is applied to the cellulose acetate support in anyconvenient manner, such as by beading, immersion, roll application, orotherwise, the subbing operation preferably being carried out inconnection with, or as a part of, the process of making the film supportitself. It is found that a subbing solution made as above described is aclear water-white liquid in which the gelatin is completely dispersed.After the application of the subbing solution to the film support, thesupport is subjected to a temperature of about -260 F. The effect oftemperature is to decompose the trimethyl benzyl ammonium hydroxide intoa tertiary amine and an alcohol a portion of which though retained inthe gelatin layer laid down on the film has no desensitizlng or otheradverse action on the emulsion which is subsequently applied to thefilm. After the subbing operationis completed, the subbed support iscoated with the light sensitive emulsion in the usual manner.

Other gelatin solutions-suitable for the subbing of celli'nose acetateand other types of cellulose derivative supports are as follows:

Example 2 Per cent Gelatin 1.0 Tetramethyl ammonium hydroxide 0.05 Water9.8 Acetone 30.1 Methanol 59.05

Example 3 Per cent Gelatin 1.0 Tetramethyl ammonium hydroxide 0.1 Water9.9 Methanol 89.0

While we have found it convenient to illustrate our invention byreference to gelatin solutions suitable for the subbing of celluloseacetate film support, our invention is in no sense limited to thesubbing of this particular type of support, as it may be applied withequal success to the treatment of almost any type of cellulosederivative material, providing the necessary adjustments in theproportion and kind of solvent constituents used in the subbing solutionare made. As is well known to those skilled in the art, each differenttype of cellulose derivative, in general, requires a slightly differentsolvent combination. It may be pointed out at this point that the gelsubbing solution is of a somewhat different nature than a gelatinemulsion, in that it must contain components that have a solvent or atleast a softening or swelling action on the cellulose derivativematerial of the support, that is, these solvent components must wet andbite into the cellulose derivative, as otherwise it would be impossibleto anchor or stick the gelatin to the support. These solvent componentscomprise a wide range of solvents, typical example being acetone, methylalcohol, ethyl alcohol, methyl cellosolve and others. We generallyemploy an amount of tetralkyl ammonium hydroxide equal to 510% of theweight of gelatin in the subbing solution.

It will be evident that our invention has completely solved theextremely troublesome problem of obtaining the necessary degree ofdispersion of gelatin in subbing solutions without the deleterio useffects heretofore resulting from the use of corrosive volatile acids,or non-corrosive, nonvolatile acids, or decomposable organic acids. Onthe contrary, no material such as an acid which would lower the emulsionpH comes in contact with the emulsion.

The'decomposition products of the hydroxides which may remain in thefilm are of such a nature thateither they are neutral or slightly basicand do not adversely afiect the light sensitive layer. In fact it isbelieved that during the curing of the subbing layer, the decompositionproducts are substantially totally volatilized.

The use of tetralkyl ammonium hydroxides is intended in no way tosimulate the activities of bufiers since no appreciable regulation ofthe emulsion pH is possible with slightl basic tertiary amines which mayremain in the sub layer after decomposition of the quaternary ammoniumhydroxides.

The tetralkyl ammonium hydroxides are typical of the easily decomposablebasic compounds which will disperse gelatin in the manner described inour invention. However, there are other quaternary hydroxides such astetralkyl phosphonium hydroxides, tetralkyl arsoniu'm hydroxides, andtetralkyl stilbonium hydroxides which are comparably basic in nature andare contemplated for use in our invention in the manner described. Theseare decomposable with heat in a manner similar to the quaternaryammonium hydroxides.

By alkyl as used herein we mean to include substituted alkyls such asbenzyl.

While our invention is best illustrated by reference to the preparationof gelatin solutions suitable for the subbing of photographic filmsupport, it is understood that it is not limited to this particularapplication, as in its broader aspects it includes the preparation ofgelatin solutions in general in which the gelatin is dispersed in thesolvent by means of the tetralkyl ammoniium hydroxides described herein.

What we claim is new and desire to secure by Letters Patent is:

1. A gelatin solution suitable for the subbing of photographic filmsupport which comprises gelatin dispersed in an organic solvent solutionby means of a tetralkyl ammonium hydroxide decomposable temperatures of-260 F.

2. A gelatin solution suitable for the subbing of photographic filmsupport which comprises gelatin dispersed in an organic solvent solutionby means of a tetralkyl ammonium hydroxide selected from the groupconsisting of trimethyl benzyl ammonium hydroxide and tetramethylammonium hydroxide.

3. A gelatin solution suitable for the subbing of photographic filmsupport which comprises gelatin dispersed in an organic solvent solutionby means of trimethyl benzyl ammonium hydroxide.

4. A gelatin solution suitable for the subbing of photographic filmsupport which comprises gelatin dispersed in an organic solvent solutionby means of tetramethyl ammonium hydroxide.

5. A gelatin solution suitable for the subbing of a cellulose derivativephotographic film support which comprises gelatin dispersed in a mixtureof acetone, methyl alcohol, and water by means of a tetralkyl ammoniumhydroxide selected from the group consisting of trimethyl benzylammonium hydroxide and tetramethyl ammonium hydroxide.

6. A gelatin solution suitable for the subbing of a cellulose acetatephotographic film support which comprises gelatin dispersedin a mixtureof acetone, methyl alcohol, and water by means of trimethyl benzylammonium hydroxide.

7. A gelatin solution suitable for the subbing of a cellulose acetatephotographic film support which comprises gelatin dispersed in a mixtureof acetone, methyl alcohol, and water by means of tetramethyl ammoniumhydroxide.

8. The method of subbing a photographic film support which comprisesapplying thereto an organic solvent solution of gelatin in which thegelatin is dispersed by means of a dispersing agent selected from thegroup consisting of trimethyl benzyl ammonium hydroxide and tetramethylammonium hydroxide, subjecting the film to a temperature of 180-260 F.,whereby the solvents and volatile constituents are removed from thedeposited layer and the dispersing agent is decomposed intonon-corrosive compounds.

9. The method of subbing a photographic film into non-corrosivecompounds at support which comprises applying thereto an organic solventsolution of gelatin in which the gelatin is dispersed by means oftrimethyl benzyl ammonium hydroxide, subjecting the film to a.temperature of 180-260 F. whereby the solvents and volatile constituentsare removed from the deposited layer and the dispersing agent isdecomposed into non-corrosive compounds.

10. The method of subbing a photographic film support which comprisesapplying thereto an m organic solvent solution of gelatin in which thegelatin is dispersed by means of tetramethyl ammonium hydroxide,subjecting thefilm to a temperature of 180-260 F., whereby the solventsand

